1. Field of the Invention
This invention relates to a method for preventing coking in equipment used in hydrocarbon treatment processes wherein a hydrocarbon is treated at a temperature of from about 250.degree. to about 950.degree. C. to produce petroleum products, petrochemical products and/or their intermediate products. More particularly, the present invention relates to a method for preventing coking in equipment such as heat exchangers, heating furnaces, reactors, connecting pipes and the like wherein a hydrocarbon is subjected to a process for refining, separation, extraction, desulfurization, reforming, polymerization, thermal cracking, catalytic cracking, synthetic reaction or a combination of at least two of them at a temperature of from about 250.degree. to about 950.degree. C. to produce petroleum products, petrochemical products and/or their intermediate products, the method comprising supplying a coking inhibitor to said equipment to prevent coking in the equipment.
2. Description of Prior Art
In many hydrocarbon treatment processes employed in petroleum and petrochemical industries, a hydrocarbon feed is heated to high temperatures in equipment such as heat exchangers, heating furnaces, reactors, ethylene cracking furnaces and the like to achieve an intended purpose. It is known that, in such case, coke-like substances (coke-like fouling) accumulate in thick deposits inside the equipment, particularly at the high temperature portions of the equipment, causing various disadvantages such as reduction in heat conduction efficiency and hindrance of the material flow inside the equipment. In order to remove these disadvantages, operators of such equipment generally conduct decoking or cleaning for the fouled equipment at frequent intervals. This solution is very undesirable when viewed from the aspect of energy saving or process rationalization.
As examples of the hydrocarbon treatment process according to the present invention, mention can be made of an atmospheric distillation column, a vacuum distillation column, a hydrodesulfurization column, a visbreaker, a coker, an aromatic hydrocarbon extraction column, etc. In these processes, a hydrocarbon feed liable to cause polymerization and coking with relative ease is used and relatively high temperatures are further employed; therefore, the coking that occurs has been big problem and countermeasures for it have been sought.
Coking is basically brought about in the following manner. A heavy fraction in feed hydrocarbon or a heavy fraction produced by partial polymerization of feed hydrocarbon adheres to the inside walls of process equipment, is exposed to high temperatures for a long period of time and grows into a coke-like substance. As methods for suppressing the formation and accumulation of such a coke-like substance, there have been proposed, for example, a method of adding a phosphoric acid derivative (U.S. Pat. No. 4,105,540), and so forth. However, all of the hitherto proposed methods are far from satisfactory and further improvements are desired.